Storage container for water-endangering liquids

ABSTRACT

A storage container for water-endangering liquids comprises a leakage detection and restraint system. The storage container provides a container that allows for a short-notice alarm system and that minimizes the collection volume, that is to ensure that the water-endangering liquid spreads as little as possible, as well as to reduce construction and maintenance costs. The storage container is characterized by the following features: a gutter ( 4 ) surrounding the tank ( 13 ) that is directly contiguous with the outer wall ( 2 ) of the storage container and that collects leaked liquid, at least one gutter outlet ( 14 ), at least one liquid collection container ( 6 ), and at least one detection system ( 12 ) for the water-endangering liquids. The gutter outlet ( 14 ) is adapted to guide the liquid collected in the gutter ( 4 ) to the liquid collection container ( 6 ) that is provided with the detection system ( 12 ).

This application is a continuation of Ser. No. 10/468,845 filed Jan. 30,2004, now U.S. Pat. No. 7,171,978.

BACKGROUND OF THE INVENTION

The invention relates to a storage container for liquids hazardous towater, having a leak detection and retention system.

Due to legal or official regulations, storage containers for liquidshazardous to water are often equipped with collection basins that arecapable of capturing the maximum storage volume of the tank. Thesecollection basins are made of a concrete or cohesive base, possibly ofsteel. Collection basins lined with synthetic films are also known. Thesize of the collection basins requires cost-intensive maintenance. Whenproduct leaks from the tank, liquid hazardous to water spreads across alarge surface and generally triggers an alarm when leakage of largerquantities of the stored material occurs. Due to water productionrequirements, comprehensive cleaning of the collection basin anddisposal of the leaked liquid and, if applicable, the collection basinmaterial is necessary in these situations.

The object of the invention is to provide a storage container with aleak detection and retention system guaranteed to promptly trigger analarm. Furthermore, the collection volume should be minimized to reducespreading of the liquids hazardous to water as well as the costs ofconstruction and maintenance.

SUMMARY OF THE INVENTION

This object is solved by a storage container for liquids hazardous towater equipped with a leak detection and retention system and having thefollowing features:

-   -   a channel encircling the tank, which is directly adjacent to the        exterior wall of the storage container and serves to collect        leaked liquid,    -   at least one channel drain,    -   at least one liquid collection container, as well as    -   at least one detection system for the liquids hazardous to        water, wherein the channel drain is design to conduct the liquid        collected in the channel into the liquid collection container,        which is equipped with the detection system.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 depicts cross-section of an embodiment of the invention.

FIG. 2 depicts a top view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The tanks are preferably those that are cylindrical in shape, especiallythose in which the center axis of the cylinder is vertically oriented.Such tanks normally consist of a base, the vertical sidewalls, alsoknown as cylinder shell or simply shell, as well as a roof. Bothfloating roofs and fixed roofs are possible. Flat-base tanks arepreferred.

In such tanks, the base is preferably adjacent to or continues into thebase of the storage container. The connection between the base of thechannel and the base of the storage container must be designed to beliquid-tight. The inner sidewall of the channel is formed by the outerwall of the storage container or the tank shell. The cross-section ofthe channel is preferably U-shaped. The outer wall of the channel andthe base are preferably made of steel or synthetic materials, especiallyfiber-reinforced synthetic materials. The material forming the channelshould be resistant to the liquid hazardous to water.

In the event that the storage container is a fixed-roof tank,precipitation falling onto this fixed roof is collected by a suitableapparatus and drained away, so that it does not enter the channel. Tothis end, a channel system can also be installed on the tank roof, in apreferred embodiment, such that the tank shell is elevated above thetank roof. In this case, the precipitation can be drained outside thechannel through a drain, such as a pipe. In this design, the liquidcollection container and therefore the detection system is kept free ofprecipitation water from the roof area of the storage container, i.e. itis no longer necessary to account for the amount of precipitationfalling on the tank roof when measuring the retention volume of thecollection container and or channel.

The principal advantage of the present invention consists in the factthat the collection volume of the channel, in contrast to that ofcollection basins known in the art, is significantly smaller than themaximum fill volume of the storage container. The required retentionvolume of the channel is not solely a function of the size of thestorage container and/or its maximum fill volume, but rather, in aneffort to minimize safety risks, is determined in large part by theassumption of a fictitious leak surface, on the one hand, and, on theother hand, by the existing infrastructure, which makes it possible totake suitable corrective action within a specific period of time. Theinfrastructure includes keeping suitable equipment as well asappropriate personnel on hand so that, in the event of actual productleakage, appropriate organizational and logistic measures can beinitiated to properly and promptly remove the leaked liquid, drain theaffected systems, if necessary, and repair the leak.

The channel is provided with a channel drain, through which the liquidfrom the channel initially reaches a liquid collection container. Saidcontainer is equipped with a detection system. The collection containerand drain can be heated, so that they can be kept free of ice in thewater. The liquid collection container is preferably provided with anelevated drain and/or overflow mechanism. To prevent liquids hazardousto water that are not miscible with water from reaching the drain, acascade divider can be installed in the liquid collection containerbetween the portion into which the liquid is directed from the channeland the portion in which the drain is located.

The positioning of the divider is dependent upon whether the leakedliquid not miscible with water floats on water or sinks. The liquidcollection container is equipped with a detection system, which ispreferably disposed in the liquid collection container. This detectionsystem is preferably one that detects non-conductive organic liquidsthat float on water, in the event that petroleum or petroleum productsare stored in the tank. The channel drain is provided with a lock thatautomatically closes if the detection system emits a positive signal.Commercially available systems can be used as the detection system. Asuitable system is, for example, a system comprising floats and a sensorwhose electric resistance changes when the position of the float changesas a result of lightweight liquid floating on the water.

In practice, such a detection emits a positive signal at a specificlayer thickness of, for example, 4-6 mm, normally triggering an alarm,either locally or at a measuring station. At the same time, the lockdisposed in the channel drain is closed. This prevents liquids hazardousto water from flowing of the channel. The alarm prompts the operatingpersonnel to check the storage container. In the event of actual leakageof liquid, suitable organizational and logistic measures can beinitiated to promptly remove the leaked liquid, drain the affectedsystems, and repair the leak. The channel is preferably provided withdevices that permit removal of the leaked liquid collected in thechannel in a manner that is not hazardous to the environment or towater. In comparison to fill volumes of up to approx. 100,000 m3 inlarge flat-base tanks, the leak detection system is already capable ofdetecting small amounts of leaking liquids, such as those less than 10l.

The connector pieces located on the tank for lines to supply and removeproducts or to connect other fixtures are preferably disposed verticallyabove the channel, so that, if leaks occur in these connections, theleaking liquid will also collect in the channel. To ensure that thisleaking liquid is detected as quickly as possible, these connectorpieces are preferably disposed in proximity to the channel drain and/orthe liquid collection container. Preferably several liquid collectioncontainers are disposed around the tank. This shortens the path betweena potential leakage site and a collection container and, therefore, thetime between leakage of the liquids hazardous to water and itsdetection.

Due to its design, the device of the invention is excellently capable ofdetecting leaks in the region of the tank shell, as well as of capturingand retaining the leaking liquid until corrective action can be taken.

FIG. 1 depicts a device according to the invention in cross-section. Onthe right side, a portion of the tank (13) is shown with a tank base(1), a tank wall (2), and a tank roof (3). This tank is a flat-base tankwith a fixed roof. The U-shaped collection channel (4) is disposed onthe outside of the tank, which is depicted to the left of the tank wallin the figure. The right wall of the channel is formed by the tank wall(2). The base of the channel is a continuation of the tank base (1). Theleft arm of the U is formed by a sidewall vertically secured to thebase. A drain (14) with a lock (7) is inserted in said sidewall. Whenthe lock is open, liquid is directed from the channel into a collectioncontainer (6) through this drain. Said collection container is equippedwith a detection system (12). To ensure that floating lightweight liquidcannot escape from the collection container through the drain (11), acascade divider (10) is installed into said collection container. Saiddivider protrudes above the surface of the liquid but does not extend tothe base. To collect the precipitation water falling onto the fixedroof, the tank wall is elevated above the tank roof (3) by placing asegment of material (5) onto it. As a result, the precipitation waterfalling onto the fixed roof cannot flow down from the roof onto the tankshell, but instead is initially collected on the tank roof and is thendrained away from the tank roof and over the channel (4) through a pipe(8). In the side wall (2) of the tank there is a connector piece (9) towhich, for example, a line for filling or draining the tank can beconnected.

FIG. 2 depicts a device according to the invention in a top view. Inthis case, there are several connector pieces (9), which are arranged soas to be in proximity to the collection container (6).

1. A storage container for liquids hazardous to water comprising: (a) a storage tank; (b) a retention system comprising: (i) a channel encircling the tank and directly adjacent to an exterior wall of the tank which channel serves to collect leaked liquid, (ii) at least one channel drain, and (iii) at least one liquid collection container; and (c) at least one detection system; wherein the channel drain is positioned to conduct liquid collected in the channel into the liquid collection container and wherein the liquid collection container is equipped with the detection system and wherein total retention volume of the retention system is less than maximum fill volume of the tank.
 2. A storage container according to claim 1, wherein the channel drain is provided with a lock, which is closed when the detection system emits a positive signal.
 3. A storage container according to claim 1, wherein the liquid collection container is provided with a drain and a cascade divider.
 4. A storage container according to claim 1, wherein the tank is equipped with at least one connector piece for a line configured for supply and removal of products or for other fixtures, wherein the connector piece is disposed vertically above the channel.
 5. A storage container according to claim 1, wherein the detection system is configured for detection of non-conductive organic liquids that float on water. 